Preparation method of chalcopyrite sulfur isotope standard substance by secondary ion mass spectrometry

Abstract

The invention provides a preparation method of a chalcopyrite sulfur isotope standard substance based on secondary ion mass spectrometry, which comprises the following steps: cleaning and drying a high-purity iron wire, putting the iron wire into a high-pressure kettle with a polytetrafluoroethylene lining, and adding hydrochloric acid to obtain a ferrous chloride solution; adding anhydrous copper chloride to form a mixed solution; slowly injecting the mixed solution into a boiling ammonium sulfide solution under a reflux condensation condition to obtain a black suspension; centrifuging to obtain black precipitate, washing and drying, quickly heating to 210-220 DEG C, reacting for 1-12 hours at a constant temperature to obtain bronze powder, performing ball milling on the bronze powder and absolute ethyl alcohol under inert gas, separating slurry, drying, and pressing into a cylinder; and wrapping and sealing the sample powder cylinder by using polytetrafluoroethylene or an inert metal sheet, assembling the sample powder cylinder in a high-pressure module, and performing high-temperature and high-pressure sintering, target preparation and polishing. The method solves the problems that the chalcopyrite standard substance is difficult to obtain and the uniformity cannot meet the analysis requirement of higher spatial resolution in the current secondary ion mass spectrometry analysis test activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of mineral analysis and testing, and particularly relates to a method for preparing a chalcopyrite sulfur isotope reference material for secondary ion mass spectrometry. Background Art

[0002] Chalcopyrite is a common metal sulfide in nature and is widely present in various hydrothermal deposits. Secondary ion mass spectrometry (SIMS) is a surface analysis method with high sensitivity and high spatial resolution. The analysis of the composition and distribution of sulfur isotopes in chalcopyrite by secondary ion mass spectrometry has been widely used to study the temperature and pressure conditions of the ore-forming process, the source of ore-forming fluids, and the ore deposit evolution process of related ore deposits. During the analysis and testing process of secondary ion mass spectrometry, reference materials are required to calculate and calibrate the analysis results. For reference materials, not only the homogeneity at a small scale (nanoscale) is required, but also the matrix matching between the reference material and the sample to be measured, that is, the consistency in chemical composition and crystal structure. Currently, the reference materials used in the secondary ion mass spectrometry analysis of chalcopyrite are all samples with relatively uniform isotope compositions selected from natural chalcopyrite, and there is no artificially prepared chalcopyrite sulfur isotope reference material suitable for SIMS analysis. However, the problems with using natural samples as reference materials are as follows: 1. Natural samples with uniform isotope compositions that meet the requirements are extremely scarce, and it can be said that only one in ten thousand can be selected. In order to find such samples, researchers in related fields often have to spend a huge amount of time and effort selecting the natural samples obtained; 2. The sulfur isotope composition in natural samples cannot be artificially controlled; 3. With the further improvement of the analysis spatial resolution, it is becoming increasingly difficult to obtain natural samples that meet the homogeneity requirements. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a chalcopyrite reference material to solve the problems of difficult acquisition of chalcopyrite reference materials and inability to meet the requirements of higher spatial resolution analysis in current secondary ion mass spectrometry analysis and testing activities.

[0004] To solve the above problems, the present invention is specifically realized through the following technical solutions:

[0005] 1) Take an appropriate amount of high-purity iron wire, place it in dilute hydrochloric acid and ultrasonically clean it for 5 - 10 minutes, then wash it with ultrapure water; after drying, weigh it, place it in a high-pressure autoclave with a polytetrafluoroethylene liner, add an appropriate amount of hydrochloric acid, and place it in an oven at 120 - 180 °C for reaction for 12 hours to obtain a fresh ferrous chloride solution; weigh an appropriate amount of anhydrous copper chloride and dissolve it in this solution to form a mixed solution with an Fe / Cu molar ratio of 1:1;

[0006] 2) Under rapid stirring, use a peristaltic pump to slowly inject the above mixed solution into a boiling ammonium sulfide solution under a condensing reflux condition to obtain a black suspension;

[0007] 3) Centrifuge the suspension obtained in step 2) to obtain a black precipitate, and wash the black precipitate multiple times with deoxygenated deionized water and absolute ethanol in sequence;

[0008] 4) Place the precipitate obtained after washing in step 3) into a tubular vacuum furnace for vacuum drying, and vacuum dry at 40 - 60 °C for 1 - 6 h;

[0009] 5) After drying, quickly heat the tubular furnace of the vacuum furnace to 210 - 220 °C within 10 - 30 min, and then carry out a constant temperature reaction for 1 - 12 h to obtain a bronze-colored powder;

[0010] 6) Take out the powder obtained in step 5, put it together with an appropriate amount of absolute ethanol and a small amount of grinding balls into a ball milling jar, then evacuate the ball milling jar and introduce an inert gas, and then use a planetary ball mill to mill for 10 minutes;

[0011] 7) After ball milling, separate the slurry and dry it in a vacuum environment at 80 - 200 °C for 1 - 4 hours;

[0012] 8) Press the dried powder into a cylindrical shape in a powder press to obtain a sample powder cylinder;

[0013] 9) Wrap and seal the sample powder cylinder with polytetrafluoroethylene or an inert metal sheet to obtain a sample assembly;

[0014] 10) Assemble the sample assembly in a high-pressure module and place it in a six-anvil press for high-temperature and high-pressure sintering, with a pressure of 0.5 - 2 GPa and a temperature of 180 - 360 °C;

[0015] 11) Take out the sintered sample, divide it, take a small amount to calibrate the sulfur element isotope ratio, and polish the remaining part to make a target, thus obtaining the chalcopyrite reference material. Description of the Drawings

[0016] Figure 1 It is the X-ray diffractometer image of Example 1;

[0017] Figure 2 It is the measurement result of Example 2. Detailed Embodiments

[0018] The specific technical solutions of the present invention are described in combination with the embodiments.

[0019] Example 1

[0020] Cut a small amount of the final sample prepared by this method and crush it to 200 mesh in an agate mortar, and use a powder X-ray diffractometer to characterize its crystal structure. Use CuKα ray (λ = 0.5146 nm), the scanning rate is 5 ° / min, and the 2θ measurement range is 20 - 70 °. AsFigure 1 As shown, the results show that the prepared bulk is pure-phase chalcopyrite.

[0021] Example 2

[0022] In-situ sulfur isotope analysis was performed on the prepared chalcopyrite bulk using a CAMECA NanoSIMS 50L. Before analysis, the sample was cleaned and then coated with a gold layer about 20 nm thick. A ~150 pA Cs + ion beam with an energy of 16 keV was rasterized over an area of 5*5 μm 2 for 150 s as the pre-sputtering time to remove the gold coating and possible contaminants, and then the secondary ion beam auto-alignment process was carried out. A Faraday cup with a 10 11 Ω preamplifier resistance was used to measure 32 S - and 34 S - ions for 300 cycles, with a duration of 0.54 s for each cycle. The total analysis time including pretreatment was approximately 7 min per measurement. The measured results are as shown Figure 2 in. δ 34 S = 17.4 ± 0.16‰ (2SD, n = 40), indicating that the prepared sample has good uniformity.

[0023] Using the chalcopyrite reference material prepared in the present invention, in-situ analysis of the sulfur isotope composition of the natural chalcopyrite reference material HTS4-6 was performed using a CAMECA NanoSIMS 50L. The obtained results are consistent with its recommended value within the error range, indicating that the matrix effect between the chalcopyrite reference material in the present invention and natural chalcopyrite can be ignored.

Claims

1. A method for preparing chalcopyrite sulfur isotope standard material for secondary ion mass spectrometry, characterized in that: The high-purity iron wire is cleaned and dried, and then placed in a polytetrafluoroethylene-lined autoclave, and hydrochloric acid is added to obtain a ferrous chloride solution; anhydrous cupric chloride is added to form a mixed solution; The mixed solution was slowly injected into boiling ammonium sulfide solution under condensation reflux conditions to obtain a black suspension; The black precipitate is obtained by centrifugation. After washing and drying, the temperature is quickly raised to 210-220°C and the reaction is carried out at a constant temperature for 1-12 hours to obtain a bronze powder and anhydrous ethanol, which are ball-milled under an inert gas, the slurry is separated, dried, and pressed into a cylindrical shape; the sample powder cylinder is wrapped and sealed with polytetrafluoroethylene or an inert metal sheet, assembled in a high-pressure block, sintered at high temperature and high pressure, and polished.

2. The method for preparing chalcopyrite sulfur isotope standard material for secondary ion mass spectrometry according to claim 1, characterized in that: The specific steps include: 1) Take an appropriate amount of high-purity iron wire, place it in dilute hydrochloric acid for ultrasonic cleaning for 5-10 minutes, and then use ultrapure water to clean it; weigh it after drying, place it in a polytetrafluoroethylene-lined autoclave, add an appropriate amount of hydrochloric acid, place it in a 120-180°C oven to react for 12 hours, and obtain a fresh ferrous chloride solution; weigh an appropriate amount of anhydrous cupric chloride and dissolve it in the solution to form a mixed solution with a Fe / Cu molar ratio of 1:1; 2) Under rapid stirring, using a peristaltic pump, slowly inject the mixed solution into the boiling ammonium sulfide solution under condensation reflux conditions to obtain a black suspension; 3) centrifuging the suspension obtained in step 2) to obtain a black precipitate, and washing the black precipitate multiple times with deoxygenated deionized water and anhydrous ethanol in sequence; 4) placing the precipitate obtained after washing in step 3) into a tubular vacuum furnace for vacuum drying at 40-60° C. for 1-6 hours; 5) After drying, the vacuum tube furnace is rapidly heated to 210-220° C. within 10-30 min, and then the reaction is carried out at a constant temperature for 1-12 h to obtain a bronze powder; 6) Take out the powder obtained in step 5, put it into a ball mill with an appropriate amount of anhydrous ethanol and a small amount of grinding balls, then evacuate the ball mill and introduce inert gas, and then use a planetary ball mill to ball mill for 10 minutes; 7) After ball milling, separate the slurry and dry it at 80-200° C. for 1-4 hours under vacuum; 8) Pressing the dried powder into a cylindrical shape in a powder tablet press to obtain a sample powder cylinder; 9) Wrapping and sealing the sample powder cylinder with polytetrafluoroethylene or an inert metal sheet to obtain a sample assembly; 10) Assemble the sample components in a high-pressure assembly and place them in a six-sided anvil press for high-temperature and high-pressure sintering at a pressure of 0.5-2 GPa and a temperature of 180-360°C; 11) The sintered sample is taken out, and a small amount is taken for calibration of its sulfur isotope ratio after segmentation, and the remaining part is used for target preparation and polishing, thereby obtaining the chalcopyrite standard material.

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